The present invention relates to an automatic sample positioning mechanism of an analyzer.
Conventionally, the method shown in FIGS. 6(a)-6(d) is used to grasp a sample container for automatic sampling. In FIG. 6(a), robot fingers 1 for picking up a container 2, previously placed on a sample tray 3, descent to a predetermined position low enough to grasp container 2, shown in FIG. 6(b), and the tips of robot fingers 1 close like a pair of tweezers and grasp the container as shown in FIG. 6(c). Then, referring to FIG. 6(d), the robot fingers raise and carry the container while grasping the container, and place the container in the sample container position inside the analyzer.
Thermal anzlyzers such as DSC, DTA, and TG are typical examples of the analyzers using these kinds of containers. Generally, many of the containers used for exterior form. On the other hand, the technology which is generally used in that a robot mechanism is installed in these analyzers for automatic sampling in order to automate the process of placing the sample container in the analyzer. In this technology, a plurality of the sample containers 2 are prepared beforehand and placed on the sample tray 3, and the robot mechanism carries and exchanges the containers one after another.
Though the containers are generally placed on the sample tray 3 manually the containers 2 placed on the sample tray 3 are grasped by the robot fingers 1 of the robot mechanism, so that the containers should be placed manually in predetermined positions. Therefore, it is a common practice to provide a cavity of suitable size for each sample container on the sample tray. This makes it easier to place sample containers 2 in predetermined positions on the sample tray manually, and prevents the sample containers 2 from deviating from the predetermined positions easily as a result of movement of the sample tray 3.
As shown in FIG. 1(c) and FIG. 2(a), however, when a sample container 2 is placed manually on a sample tray 3, the position of sample container 2 sometimes deviates slightly from the center of the cavity in the sample tray 3 and is placed obliquely to the surface of the sample tray 3.
In the above case, when robot fingers 1 of an automatic sampler grasp the sample container 2 by the conventional method, the robot fingers 1 often pick up and carry the sample container 2 while it continues to be oriented obliquely. There is thus the drawback that if the sample container is carried in the above condition, there is a strong possibility that the robot fingers will drop the sample container 2 while carrying it. Accordingly the sample container 2 is placed in the analyzer at a distance from the desired position.